diff --git a/biscuit/apps/chronos/forms.py b/biscuit/apps/chronos/forms.py
index 2ad9b84de1c4a5ea1499dd31ea257dafd124726d..f9f304ed6093edf5a997d98f8a294015a319b1b1 100644
--- a/biscuit/apps/chronos/forms.py
+++ b/biscuit/apps/chronos/forms.py
@@ -4,7 +4,7 @@ from django.utils.translation import ugettext_lazy as _
 
 from biscuit.core.models import Person, Group
 
-from .models import Room
+from .models import Room, LessonSubstitution
 
 
 class SelectForm(forms.Form):